1. Field of the Invention
The present invention relates to the field of liquid crystal displaying techniques, and in particular to a liquid crystal display panel and a pixel electrode.
2. The Related Arts
Liquid crystal displays are gradually getting wide applications as a displaying device for various electronic devices, such as mobile phones, personal digital assistants (PDAs), digital cameras, computer monitor screens, or notebook computer screens. A liquid crystal display device comprises a backlight module and a liquid crystal display panel. The liquid crystal display panel is formed of two substrates and a layer of liquid crystal filled between the substrates. The manufacturing techniques of the liquid crystal display panel are very diverse and a vertical alignment (VA) liquid crystal display panel is the most common one.
In a VA liquid crystal display panel, an aligning gap is formed in a pixel electrode of a pixel in order to have liquid crystal molecules generating a specific aligning direction. FIG. 1 is a schematic view showing a structure of VA mode liquid crystal display panel according to conventional technology. As shown in FIG. 1, a unit pixel electrode structure 1 of liquid crystal display panel comprises a data line DL, a scan line SL, a thin film transistor 114, and a pixel electrode (not shown). The pixel electrode is located in a pixel area and shows a snow flake like layout. The pixel electrode is composed of three portions, including a vertical central main trunk 111, a horizontal central main trunk 112, and branches 113 that include an angle of ±45 degrees or ±135 degrees with respect to the X-axis. The vertical main trunk 111 and the horizontal main trunk 112 equally divide the pixel area into four domains and each domain is formed by laying flat the electrode branches 113 of 45 degree inclination. As such, a snow flake like configuration of electrode that is of mirror symmetry for both upper and lower portions and left and right portions is formed. Some of the branches 113 are electrically connected to the thin film transistor 114 to transmit a voltage from the data line DL, via the thin film transistor 114, to the pixel electrode.
Further, FIG. 2 is a schematic view illustrating orientation of liquid crystal molecules with a voltage applied to the pixel electrode of FIG. 1. Referring to FIG. 2, in which the unit pixel electrode is designated at 100 and is identical to the unit pixel electrode structure 1 shown in FIG. 1, when the snow flake like pixel electrode is energized, liquid crystal 120 shows orientation that is gradually inclined from outside of the pixel electrode toward the inside and the angle of inclination is along the extension direction of the branches. The inclination directions of liquid crystal of the four domains are respectively ±45 degrees and ±135 degrees and all point to a central zone of the pixel. Specifically, as shown in FIG. 2, the angles of the orientations of liquid crystal of the four domains with respect to the x axis (the scan line) are: −135 degrees for the first quadrant, −45 degrees for the second quadrant, 45 degrees for the third quadrant, and 135 degrees for the fourth quadrant.
The liquid crystal of FIG. 1 shows an inclination angle that is inclined from outside toward inside and having an orientation pointing inward of the pixel. In such a structure of pixel electrode, the vertical main trunk 111 and the horizontal main trunk 112 at the center of the pixel electrode are both light-blocked area and this makes the transmittance of the main trunk areas 111, 112 null. Consequently, such an arrangement reduces the aperture ratio of the liquid crystal display panel.
To address the issue of aperture ratio of FIG. 1, the structure of pixel electrode shown in FIG. 3 is available. FIG. 3 is a schematic view showing another structure of VA mode liquid crystal display panel according to the conventional technology. As shown in FIG. 3, a unit pixel electrode structure 400 of liquid crystal display panel comprises a data line DL, a scan line SL, a thin film transistor 414, and a pixel electrode (not shown). The pixel electrode is also located inside the pixel area and shows a pattern that is different from that of the previously discussed pixel electrode. In this arrangement, the pixel electrode comprises a square frame 411 and electrode branches 413 located inside the frame. The plurality of electrode branches 413 forms in a center thereof an opening 412, and the opening 412 substantially divides the area of the pixel into four equal domains. Each domain is formed by laying flat the electrode branches 413 that are of inclination of 45 degrees. Further, FIG. 4 is a schematic view illustrating orientation of liquid crystal molecules with a voltage applied to the pixel electrode of FIG. 3. Referring to FIG. 4, when the pixel electrode is energized, liquid crystal 420 shows orientation that is gradually inclined from inside of the pixel electrode toward the outside and the angle of inclination is along the extension direction of the electrode branches. The inclination directions of liquid crystal of the four domains are respectively ±45 degrees and ±135 degrees and the directions point from a central area of the pixel toward four corners of the pixel area. It can be found that with the pixel electrode receiving a voltage, the liquid crystal molecules incline from inside to outside so as not to squeeze the central area. Consequently, a circuit designer is allowed to minimize the area of the central opening 412 and thus, the surface area of non-opening zone is significantly reduced and an increased aperture ratio is obtained.
Further, FIG. 5 is a schematic view illustrating orientation of liquid crystal molecules with a voltage applied to the pixel electrode of FIG. 3. It can be found by viewing FIG. 5 that although adoption of the structure of pixel electrode shown in FIG. 3 dissolve the issue of aperture ratio, yet the pattern displayed in the pixel electrode area of FIG. 5 reveals that light-blocked areas exist in the four domains defined by the pixel electrode and this indicates that the orientations of the liquid crystals within the light-blocked areas show an included angle of 0 degree or 90 degrees with respect to the x axis. As a consequence, a phenomenon of disclination line is resulted in the whole pixel electrode and the transmittance of panel is reduced.